Low-power touch button sensing system

ABSTRACT

A capacitance sensing circuit receives an application of a power supply. The capacitance sensing circuit controls a switch circuit to connect the power supply to a processing device responsive to the application of the power supply. The capacitance sensing circuit receives, via a control interface and from the processing device, control information to configure the capacitance sensing circuit. The capacitance sensing circuit disconnects the power supply from the processing device subsequent to receiving the control information.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/175,856 filed on Jun. 15, 2015, the contents of which are herebyincorporated by reference herein.

TECHNICAL FIELD

This disclosure relates to the field of sensing systems and, inparticular, to a touch button sensing system.

BACKGROUND

Computing devices, such as notebook computers, personal data assistants(PDAs), mobile communication devices, portable entertainment devices(such as handheld video game devices, multimedia players, and the like),and set-top-boxes (such as digital cable boxes, digital video disc (DVD)players, and the like) may have user interface devices, which are alsoknown as human interface devices (HID), that facilitate interactionbetween the user and the computing device. One type of user interfacedevice that has become more common is a sensing system that operates byway of touch sensing, such as capacitance sensing. A sensing system,such as a capacitance sensing system, may include a processing deviceand one or more capacitive sense electrodes. The capacitance detected ofthe capacitive sense electrodes by a processing device may change as afunction of the proximity of a touch object to the capacitive sensearray.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings.

FIG. 1 is a block diagram illustrating a low-power touch button sensingsystem, according to an embodiment.

FIG. 2 illustrates a low-power touch button sensing system with acontrol interface, according to one embodiment.

FIG. 3 illustrates a low-power touch button sensing system, according toone embodiment.

FIG. 4 illustrates a low-power touch button sensing system with a delaytimer circuit, according to one embodiment.

FIG. 5 illustrates a low-power touch button sensing system integratedinto a processing device, according to one embodiment.

FIG. 6 illustrates a low-power touch button sensing system configured toreceive an application of a power supply, according to one embodiment.

FIG. 7 illustrates a low-power touch button sensing system with touchbutton switches, according to one embodiment.

FIG. 8 is a flow diagram illustrating the operation of a low-power touchbutton sensing system, according to one embodiment.

FIG. 9A is a flow diagram illustrating the operation of a low-powertouch button sensing system, according to one embodiment.

FIG. 9B is a flow diagram illustrating the operation of a low-powertouch button sensing system, according to another embodiment.

FIG. 10 is a block diagram illustrating an electronic system including aprocessing device and low-power touch button circuit, according toanother embodiment.

DETAILED DESCRIPTION

Electronic devices, such as processing devices, consume electric power.Power sources, such as batteries or wireless power signals, forelectronic devices may have small and relatively finite capacities.Electronic devices using power sources with small and finite capacitiesmay quickly consume power budgets and be rendered non-functional. Manypower saving techniques such as low-power modes or sleep modes may beinappropriate, costly, or consume too much power.

The present disclosure addresses the above-mentioned and otherdeficiencies by detecting, by a capacitance sensing circuit, a presenceof a touch object proximate to a touch button and controlling a switchcircuit to connect a power supply to a processing device responsive tothe detected touch. The capacitance sensing circuit consumes a smallamount of current during operation.

In one embodiment, a capacitance sensing circuit receives an applicationof a power supply at power-up. For example, a capacitance sensingcircuit may be disconnected from a power supply until, at power-up, abattery is applied to the capacitance sensing circuit. After theapplication of the power supply, the capacitance sensing circuitcontrols a switch circuit to connect the power supply to a processingdevice. The processing device receives power from the power supply andwakes up to perform a power-up routine including sending, via a controlinterface to the capacitance sensing circuit, control information toconfigure the capacitance sensing circuit. The capacitance sensingcircuit is configured to respond to events, such as a presence of atouch object detected proximate to a touch button or a sequence oftouches proximate to one or more touch buttons, by connecting ordisconnecting the power supply and the processing device. Subsequent toreceiving the control information, the capacitance circuit disconnectsthe power supply from the processing device and waits until an event,such as a detected touch, to reconnect the power supply and theprocessing device.

In another embodiment, the capacitance sensing circuit connects thepower supply to the processing device independent of a detected touch.The capacitance sensing circuit may control the switch circuit toconnect the power supply to the processing device responsive to a timerevent. For example, the capacitance sensing circuit may include a delaytimer circuit that counts clock pulses. After a predetermined number ofclock pulses, the delay timer may signal to the capacitance sensingcircuit to connect the power supply to the processing device.

In another embodiment, multiple touch buttons may be coupled together toform a composite button, for example when the capacitance sensingcircuit is controlling the switch circuit to disconnect power from theprocessing device. The touch buttons may, for example, be capacitivebuttons. The capacitance sensing circuit may measure a signal indicativeof a single capacitance for the composite button to detect a presence ofa touch object proximate to the composite button. The capacitancesensing circuit may be configured to connect the power supply to theprocessing device responsive to detecting a presence of a touch objectproximate to the composite button. Alternatively, the capacitancesensing circuit may detect a presence of a touch object proximate to thecomposite button and in response, measure signals indicative of theindividual capacitance of multiple touch buttons to detect the presenceof a sequence of touches. For example, capacitance sensing circuit maycouple multiple touch buttons together to detect a presence an initialtouch, and then disconnect some or all of the touch buttons and measurethem individually to identify which touch button or touch buttons havebeen touched. After the presence of the initial touch is detected, thecapacitance sensing circuit measures the individual buttons to detect asequence of touches. When a predetermined sequence of touches isdetected, such as a sequence of touches representative of a password orthe like, the capacitance sensing circuit connects the power supply tothe processing device by controlling the switch circuit.

FIG. 1 is a block diagram illustrating a low-power touch button sensingsystem, according to an embodiment. Low-power touch button sensingsystem 100 includes power supply 116 external to the low-power touchbutton circuit 101. In another embodiment, another power supply (notshown) may power low-power touch button circuit 101. Low-power touchbutton circuit 101 may measure for a touch, also referred to as apresence of a touch object proximate to a touch button, such as touchbutton 114. When low-power touch button circuit 101 senses a qualifiedtouch event (e.g., a measurement value of touch button 114 that exceedsa touch threshold value), the capacitance sensing circuit 110conditionally controls switch circuit 112 to provide power to anotherelectronic device, such as processing device 118. It should beappreciated that capacitance sensing circuit 110 may perform all thefunctions and includes similar components as discussed with respect tolow-power touch button circuit 101.

Power supply 116 may supply electric power to all or part of one or moreelectronic devices, such as a low-power touch button circuit 101 and orprocessing device 118. Power supply 116 may be external to an electronicdevice (e.g., low-power touch button circuit 101 and or processingdevice 118) and when electrically connected to the electronic device,supplies power for the entire electronic device, including the multiplecircuits of the electronic device. Power supply 116 may comprise abattery or an energy harvesting device or another source of electricalpower.

An external switch (not shown), for example, may connect and disconnectpower supply 116 from low-power touch button circuit 101. When the powersupply 116 connects to the low-power touch button circuit 101 (i.e., thepower supply 116 having been previously unconnected to low-power touchbutton circuit 101), low-power touch button circuit 101 includingcapacitance sensing circuit 110 receives an application of the powersupply 116. For example, the application of the power supply 116 mayoccur at power-up of low-power touch button circuit 101 when powersupply 116 changes from being disconnect from the low-power touch buttoncircuit to being connected to low-power touch button circuit 101. Powersupply may be any power source capable of supplying power. In oneembodiment, power supply 116 is low-capacity power source such asbattery, wireless signal, or the like.

Low-power touch button circuit 101 includes switch circuit 112. Switchcircuit 112 may be an electric circuit capable of being controlled toconnect and disconnect power supply 116 from an electronic device, suchas processing device 118. Switch circuit 112 may be internal or externalto low-power touch button circuit 101. Switch circuit 112 may be adiscrete or integrated circuit. Switch circuit 112 may be a power switchsuch as a switch including a power metal-oxide-semiconductorfield-effect transistor (MOSFET), a bipolar junction transistor (BJT),silicon-controlled rectifier (SCR), or other switch circuit. Switchcircuit 112 may be connected to capacitance sensing circuit 110 viaswitch control 180. For example, capacitance sensing circuit 110 maycontrol the gate voltage of switch circuit 112 to open or close switchcircuit 112 allowing power supply 116 to be connected or disconnected toprocessing device 118.

Low-power touch button circuit 101 may include capacitance sensingcircuit 110. Capacitance sensing circuit 110 may be used to measuretouch button 114 to detect a presence of a touch object proximate totouch button 114. In one embodiment, capacitance sensing circuit 110 maybe a low-power device that consumes less than 100 nanoamperes (nA)during operation (i.e., average current consumption over a time periodsuch as a second, minute, hour, or day). In one embodiment, capacitancesensing circuit 110 may operate in a normal mode. In normal mode, thecapacitance sensing circuit 110 may operate for a percentage of a timeperiod in an idle state. For example, in an idle state, the oscillatorof the bias generator, oscillator, time circuit (e.g., BOT circuit 330of FIG. 3) runs but the analog front end (e.g., AFE 332 of FIG. 3) isturned off. In the idle state, the capacitance sensing circuit 110 mayconsume, for example, approximately 10 nA for 91% of the time period. Atintervals, for example every second, minute, day, etc., capacitancesensing circuit 110 may change from an idle state to an active state. Inan active state, the capacitance sensing circuit 110 may turn on AFE 332to measure for a signal indicative (e.g., current and or voltage) of thepresence of a touch object proximate to touch button 114. In the activestate, capacitance sensing circuit 110 may consume, for example,approximately 1 microampere (μA) for 9% of the time period. In the aboveexample, the capacitance sensing circuit 110 consumes approximately anaverage of 99.1 nA during operation (e.g., 10 nA×91%+1 μA×9%) during thetime period. It should be appreciated that the percentage of the timeperiod that the capacitance sensing circuit 110 is in the active statemay be any percentage (e.g., 100%, 50%, 10%, 5%, 1%, 0.1%, etc.). Theminimum average power consumption during operation of low-power touchbutton circuit 101 may be approximately the current consumption duringthe idle state. Low-power may refer to the average current consumptionover a time period of a device, such as capacitance sensing circuit 110or low-power touch button circuit 101, during operation and at anyoperating voltage. In one embodiment, capacitance sensing circuit 110may consume less than 100 nA during operation. It should also beappreciated that capacitance sensing circuit 110 may consume less ormore than an average of 100 nA during operation, such as 20 nAm 200 nA,500 nA, etc.

In normal mode, if no presence of a touch object is detected,capacitance sensing circuit 110 may return to an idle state, and waitfor another interval to measure for a presence of a touch object. If apresence of a touch object is detected, capacitance sensing circuit 110may control switch circuit 112 to connect power supply 116 to processingdevice 118. It should be noted that low-power touch button circuit 101may be configured to control switch circuit 112 in response to anynumber of detected touch combinations or other events (e.g., timerevents or delay events). Capacitance sensing circuit 110 will be furtherdescribed in the following figures, such as FIGS. 2-7. It should beappreciated that one or touch buttons may be present and that a presenceof a touch object on one or more of the touch buttons may not causecapacitance sensing circuit 110 to connect and or disconnect powersupply 116 and processing device 118. For example, capacitance sensingcircuit 110 may keep the power supply 116 disconnected from processingdevice 118 when a presence of a touch in on the other touch buttons(e.g., touch buttons (not shown) in addition to touch button 114 (e.g.,capacitance sensing circuit 110 may not measure for a presence of atouch on the other touch buttons).

Touch button 114 may be electrically connected to low-power touch buttoncircuit 101. Touch button 114 may be part of low-power touch buttoncircuit 101 (e.g., a pad or trace on a board or on chip) or a discretecomponent (e.g., connected to low power touch button circuit 101 via aconnecting terminal). The touch button 114 may be any type of buttonthat senses a touch using an electric signal. Examples of touch button114 may be a capacitive button, a resistive button, an optical button,or the like. Although one touch button 114 is illustrated, it should beappreciated that one or more touch buttons may be used.

In one embodiment, touch button 114 is a capacitive button. Thecapacitive button may be a self-capacitance button or a mutualcapacitance button. The capacitive button may include one or moreconductive electrodes. A presence of a touch object proximate to acapacitive button changes the capacitance associated with the capacitivebutton. The signal representing the capacitance associated with thebutton may be measured, and the measured signal indicative ofcapacitance may be used to determine a presence of a touch objectproximate to the capacitive button.

A touch object (not shown) refers to a conductive item capable ofconducting electric charge. A passive touch object refers to aconductive item physically unconnected (e.g., lacking an electric wire,electric cable, etc.) to a power supply (e.g., battery, physicalcapacitor, etc.) and or a conductive item unable to generate and orstore an electric signal. In one example, a passive touch object may bea part of a human body, such a human hand and or human finger. Inanother example, a passive touch object may be a passive stylus.

Processing device 118 may include a microprocessor or central processingunit, a controller, special-purpose processor, digital signal processor(DSP), a state machine, an application specific integrated circuit(ASIC), a field programmable gate array (FPGA), or the like. In oneembodiment, processing device 118 may be any electronic device capableof consuming electric power, such as a mobile phone, tablet, camera, orother portable electronic device.

FIG. 2 illustrates a low-power touch button sensing system with acontrol interface, according to one embodiment. Low-power touch buttonsystem 200 includes the same or similar components and functionality asdescribed above and additionally includes control interface 220. Thecontrol interface 220 may be an interface to exchange information (e.g.,data) to and from low-power touch button circuit 101. Control interface220 may be a serial interface (such as SPI or I2C) or a parallelinterface. Processing device 118 may use control interface 220 to readinformation from or write information to low-power touch button circuit101.

Low-power touch button circuit 101 may include volatile memory and ornon-volatile memory. Volatile memory, such as registers, andnon-volatile memory may be set to a default configuration on a power-upand or set from control information received via control interface 220.

In one embodiment, as described above, a low-power touch button circuit101 receives an application of a power supply 116 at power-up. After theapplication of the power supply 116, the capacitance sensing circuit 110automatically controls a switch circuit 112 to connect the power supply116 to a processing device 118. The processing device 118 receives powerfrom the power supply and performs a power-up routine including sending,via a control interface 220 to the capacitance sensing circuit 110,control information to configure the capacitance sensing circuit 110 viaa control interface 220.

The control information may include data indicating events for which thelow-power touch button circuit 101 is to turn-off and connect ordisconnect power supply 116 from processing device 118. For example, thecontrol information may be loaded into registers of the low-power touchbutton circuit 101. The control information may indicate what type oftouch events (e.g., a single touch, a pattern of touches, multiplestouches, the time between touches, touch threshold values, etc.)detected by low-power touch button circuit 101 cause the low-power touchbutton circuit 101 to connect power supply 116 to processing device 118.The control information may indicate what type of timer event (e.g.,predetermined and or programmed clock cycles) the low-power touch buttoncircuit 101 is to measure for a presence of a touch object proximatetouch button 114 and or connect power supply 116 to processing device118 independent of a detected touch. The control information may alsoindicate what type of disconnect event (e.g., signal from processingdevice 118, number of clock cycles, no touch detected, etc.) thelow-power touch button circuit 101 is to disconnect the power supply 116from processing device 118. The control information may indicate whattype of event (e.g., touch event, timer event, etc.) low-power touchbutton circuit 101 is to send a signal, for example, interrupt signal toprocessing device 118. For example, processing device may be connectedto power supply 116 but operating in a sleep mode. When low-power touchbutton circuit 101 detects a touch, low-power touch button circuit 101may send an interrupt signal to processing device 118 to, for example,wake up processing device 118. It should be appreciated that the controlinformation may include any number of events to cause the low-powertouch button circuit 101 to perform functions, such as but not limitedto, change modes, connect and disconnect power supply 116, send andreceive information via control interface 220, and or measure for apresence of a touch object proximate to touch button 114, among otherfunctions.

In another embodiment, processing device 118 may use the controlinterface 220 to send control information to test the functionality ofthe low-power touch button circuit 101. In still another embodiment,processing device 118 may use the control interface 220 to send controlinformation that informs the low-power circuit to disconnect powersupply 116 from the processing device 118. In still another embodimentprocessing device 118 may use the control interface 220 to receiveinformation about which of the touch buttons currently have a touchobject in proximity.

FIG. 3 illustrates a low-power touch button sensing system, according toone embodiment. Low-power touch button sensing system 300 functions andincludes similar components as described above with respect to FIGS. 1and 2. Switch circuit 312 is illustrated as a discrete componentseparate from capacitance sensing circuit 110, but may alternatively bea discrete semiconductor device contained in a single multi-chip packageas capacitive sensing circuit 110. Capacitance sensing circuit 110 mayperform similar function as low-power touch button circuit 101, asdescribed herein, and vice versa. Capacitance sensing circuit 110 may bea discrete chip, as illustrated, or integrated into another device, suchas processing device 118. Touch button 114 and touch button 338 areillustrated as being off chip.

Capacitance sensing circuit 110 includes a bias generator, oscillator,timer (BOT) circuit 330, analog front end (AFE) 332, control circuit340, and power-on-reset (POR) 348. Processing device 118 includes POR370 and additional communication lines, such as interrupt 356 and clock354 connecting to capacitance sensing circuit 110. AFE 332 includes anoscillator and voltage and or current references 334 and capacitancesensor 336 to measure a presence of a touch object proximate to touchbutton 114 and or touch button 338. Control circuit 340 includes statemachine 342, serial communication circuit 344, and registers 346.Capacitance sensing circuit 110 may be connected to processing device118 via POR 370, interrupt 356, clock 354 and control interface 220, andsend and or receive corresponding signals via the connections.

In one embodiment, capacitance sensing circuit 110 may operate in anyone of multiple operational modes. For example, capacitance sensingcircuit may operate in normal mode, disable mode, or continuous mode. Innormal mode, as discussed above with respect to FIG. 1, capacitancesensing circuit 110 may operate in an idle state where the oscillatorruns and periodically, switch to an active state where capacitancesensing circuit 110 measures one or more touch buttons to detect apresence of a touch object . When a qualified touch event is detected,e.g., the measured value of the touch exceeds a touch threshold valueindicative of a presence of a touch object proximate to a touch button,capacitance sensing circuit 110 may connect power supply 116 toprocessing device 118 and or generate an interrupt signal. The interruptsignal may be sent to processing device 118 via interrupt 356.Additionally in normal mode, a timer event may be periodically generated(e.g. from delay timer circuit 482 of FIG. 4) independent of a qualifiedtouch event. Responsive to the timer event, capacitance sensing circuit110 may connect power supply 116 to processing device 118 and orgenerate an interrupt signal.

In disable mode, the oscillator of BOT circuit 330 may continue to runand the state machine 342 may be disabled. In continuous mode,capacitance sensing circuit 110 may continuously measure for a presenceof a touch object proximate to the touch button 114 and or touch button338. After each reading, capacitance sensing circuit 110 may updateregisters 346 with the measurement value. When a qualified touch eventis detected, capacitance sensing circuit 110 may connect power supply116 to processing device 118 and or generate an interrupt signal.

BOT circuit 330 includes a timer circuit that sends a clock signal viaclock line 352 after some interval. The interval may be hardcoded intoBOT circuit 330 or programmed using, for example, the controlinformation received from processing device 118. Control circuit 340receives the clock signal via clock line 352 and in response, turns onAFE 332. AFE 332 measures for a presence of a touch object proximate tothe touch button 114 and or touch button 338. Measurement data may bereceived by control circuit 340 from AFE 332 and stored in registers 346and or be sent to processing device 118 via control interface 220. Themeasurement data may be sent to state machine 342. State machine 342 mayuse the measurement data to determine if the measurement data qualifiesas a state event (also referred to as an event), such as a qualifiedtouch event. If the state machine 342 determines for that themeasurement data is a qualified touch event, state machine may execute acorresponding action such as send a control signal via switch control180 to open or close switch circuit 112 and or send an interrupt signalvia interrupt 356. It should be appreciated that state machine 342 maybe programmed with any number of qualifying events (e.g., touch event,timer event, multi-touch event, non-touch event, etc.), and is notlimited to the events discussed herein.

BOT circuit 330 may provide a bias current and voltage to the AFE 332and or control circuit 340. Additionally, BOT circuit 330 may include anoscillator, such as a 1 kilo Hertz (kHz) oscillator or other frequencyoscillator. BOT circuit 330 may also include a timer circuit,programmable or fixed, to count clock pulses of the oscillator and senda clock signal via clock line 352 after some number of clock pulses(e.g., after a predetermined time period). BOT circuit 330 may operatewhen capacitance sensing circuit 110 in an idle state (e.g., notmeasuring for a presence of a touch object) and draw small amounts ofcurrent, for example an average of 10 nA over a time period.

FIG. 4 illustrates a low-power touch button sensing system with a delaytimer circuit, according to one embodiment. Low-power touch buttonsystem 400 may include the functionality and components as discussedabove with respect to FIGS. 1-3. Capacitance sensing circuit 110illustrates one embodiment of a circuit capable of periodicallyconnecting power supply 116 to processing device 118, independent of adetected presence of a touch object. It should be appreciated thatlow-power touch button system 400 may also include a processing device,such as processing device 118 (not shown in FIG. 4).

In one embodiment, control circuit 340 may include a delay timer circuit482, also referred to as a watch dog timer, to periodically generate acontrol signal. The delay timer circuit 482 may be clocked from anoscillator or may be a self-timed circuit such as a monostable circuit.The control signal may be sent to switch circuit 112 via switch control180. Responsive to the control signal, switch circuit 112 may open andconnect power supply 116 to processing device 118. The control signalgenerated by delay timer circuit 482 may be independent of a detectedpresence of a touch object. The period may be hard-coded or programmedby, for example, control information received from processing device118. The period may be any length such as seconds, minutes, day, years,etc.

FIG. 5 illustrates a low-power touch button sensing system integratedinto a processing device, according to one embodiment. Low-power touchbutton system 500 illustrates low-power touch button circuit 101integrated with processing device 518 on a single chip. Low-power touchbutton system 500 may include the functionality and components asdiscussed above with respect to FIGS. 1-4. The power supply (not shown)may be provided by the processing device 518. The processing device 518may enable low-power touch button circuit 101 at any time, by forexample, supplying power to low-power touch button circuit 101.Processing device 518 may use low-power touch button circuit 101 tomeasure for a presence of a touch object proximate to touch button 114and or touch button 338 by for example, setting low-power touch buttoncircuit 101 on continuous mode, as discussed above. In one embodiment,processing device 518 may provide POR 370 as an input to low-power touchbutton circuit 101 and or remove POR 348 (in FIG. 4) from low-powertouch button circuit 101.

In one embodiment, processing device 518 may use POR 370 to resetlow-power touch button circuit 101 and configure low-power touch buttoncircuit 101 using control information, as described above.

In another embodiment, processing device 518 may set the mode oflow-power touch button circuit 101 to disable, normal, or continuous bysending a signal via control interface 220.

In another embodiment, after setting the mode, processing device 518 maygo into a low-power mode or sleep mode. When low-power touch buttoncircuit 101 senses a qualified touch event, low-power touch buttoncircuit 101 may send an interrupt signal to wake up processing device518 or to cause processing device 118 to change modes. In anotherembodiment, processing device 518 may be awake (e.g., not in low-powermode) when low-power touch button circuit 101 is in disable, normal, orcontinuous mode.

FIG. 6 illustrates a low-power touch button sensing system configured toreceive an application of a power supply, according to one embodiment.Low-power touch button system 600 may include the functionality andcomponents as discussed above with respect to FIGS. 1-5. Power-up mayrefer to the application of a power supply 116 to low-power touch buttoncircuit 101 where the power supply 116 previously is disconnected fromlow-power touch button circuit 101. Power-up 690 illustrates powersupply 116 being applied to low-power touch button circuit 101 from apreviously unconnected state.

In one embodiment, power supply 116 is applied to low-power touch buttoncircuit 101. In response to the application of power supply 116, POR 680may send a signal to logic gate 681. Logic gate 681 may be any type oflogic gate, such as a logical OR gate. In response to the signal fromPOR 680, logic gate 681 sends a control signal to switch circuit 112 toconnect power supply 116 to processing device 118. In response, powersupply 116 enables POR 670 of processing device 118. POR 670 sends asignal to control information block 671. In one embodiment, controlinformation block 671 sends control information, via control interface220, to configure low-power touch button circuit 101. In anotherembodiment, control information block 671 sends control information totest low-power touch button circuit 101. In another embodiment, controlinformation block 671 sends a signal indicating low-power touch buttoncircuit is to disconnect power supply 116 from processing device 118.Capacitance sensing circuit 110 may disconnect the power supply inresponse to receiving the control information, in response to detectinga qualifying touch event, in response to receiving a signal fromprocessing device 118, or in response to any other detected event.

FIG. 7 illustrates a low-power touch button sensing system with touchbutton switches, according to one embodiment. In one embodiment, touchbutton switches 790 may be used to couple some or all of the touchbuttons 791-794 into a composite button. In one embodiment, some but notall of the touch buttons 791-794 may be capable of being coupledtogether, via touch button switches 790, to form a composite button.Low-power touch button system 700 may include the functionality andcomponents as discussed above with respect to FIGS. 1-6. Low-power touchbutton circuit 101 includes touch button switches 790 including touchbutton switch 790A, touch button switch 790B, touch button switch 790C,and touch button switch 790D connected to touch button 791, touch button792, touch button 793, and touch button 794, respectively. It should beappreciated that any number of touch button switches and any number oftouch buttons may be used. Touch button switches 790 may be part oflow-power touch button circuit 101, capacitance sensing circuit 110, orexternal to the aforementioned. Touch button switches 790 may becontrolled by low-power touch button circuit 101, processing device 118,or another device. In one embodiment, the function of the touch buttonswitches 790 is implemented within the capacitance sensing circuit 110rather than using separate switches.

In one embodiment, touch button switches 790 may be used to couplemultiple touch buttons into a composite button. Capacitance sensingcircuit 110 may measure a signal indicative a capacitance of thecomposite button to detect a presence of a touch object. For example,touch button switches 790 may all be closed to connect touch button 791,touch button 792, touch button 793, and touch button 794 to capacitancesensing circuit 110. Capacitance sensing circuit 110 may measure asignal indicative of a single capacitance for the composite button. Inone embodiment, the composite button may be sensed usingself-capacitance sensing, and the touch buttons sensed individuallyusing mutual capacitance sensing. In another embodiment, the compositebutton may be sensed using mutual-capacitance sensing, and the touchbuttons 791-794 sensed individually using self- capacitance sensing. Inyet another embodiment, the composite button and individual touchbuttons 791-794 may be sensed using the same type of capacitancesensing.

In one embodiment, touch button 791, touch button 792, touch button 793,and touch button 794 may be coupled together and measured to detect apresence of a touch object proximate to the composite button. When apresence of a touch object is detected on the composite button,capacitance sensing circuit 110 may further measure a signal indicativeof a capacitance for each of the touch buttons separately by control oftouch button switches 790. For example, capacitance sensing circuit 110may periodically measure for a presence of a touch object on thecomposite button (which may be formed from all or only some of theindividual touch buttons 791-794). Once a presence of a touch object isdetected on the composite button, capacitance sensing circuit 110 maywait to detect a password or sequence of button touches that satisfy asa qualifying event. Once the correct sequence of touches is detected,low-power touch button circuit 101 may connect power supply 116 toprocessing device 118. If the correct sequence of touches is notdetected, low-power touch button circuit 101 may continue to disconnectpower supply 116 from processing device 118. It should be appreciatedthat other types of touch buttons, other than capacitive touch buttons,may be coupled and or used together and measured to detect a presence ofa touch object.

FIG. 8 is a flow diagram illustrating the operation of a low-power touchbutton sensing system, according to one embodiment. Method 800 may beperformed by processing logic that comprises hardware (e.g., circuitry,dedicated logic, programmable logic, microcode), software (e.g.,instructions run on a processing device to perform hardware simulation),or a combination thereof. In one embodiment, low-power touch buttoncircuit 101 and or capacitance sensing circuit 110 may perform some orall the operations described herein.

Method 800 begins at block 805 where processing logic performing themethod operates capacitance sensing circuit 110 in an idle state. In oneexample, in the idle state the oscillator of BOT 330 is running and AFE332 is turned off. At block 810, processing logic changes capacitancesensing circuit 110 from an idle state to an active state to measure fora presence of a touch object proximate to a touch button, such as touchbutton 114. The change from idle state to active state may occur atintervals. In one example, BOT circuit 330 may send a clock signal viaclock 352 at intervals to control circuit 340 to turn on AFE 332 tomeasure for a presence of a touch object. The intervals may bedetermined by a timer of BOT circuit 330 that counts pulses of theoscillator of BOT circuit 330 and sends the clock signal via clock 352after a predetermined number of pulses (e.g., 1000 pulses or 1 second, 1minute, etc.). At block 815, processing logic detects a presence of atouch object proximate to a touch button, such as touch button 114. Ifno presence of a touch object is detected, processing logic returns toblock 805 and returns capacitance sensing circuit 110 to an idle state.If a presence of a touch object is detected, processing logic proceedsto block 810, where processing logic in response to detecting a presenceof a touch object controls a switch circuit 112 to connect power supply116 to processing device 118.

FIG. 9A is a flow diagram illustrating the operation of a low-powertouch button sensing system, according to one embodiment. Method 900 maybe performed by processing logic that comprises hardware (e.g.,circuitry, dedicated logic, programmable logic, microcode), software(e.g., instructions run on a processing device to perform hardwaresimulation), or a combination thereof. In one embodiment, low-powertouch button circuit 101 and or capacitance sensing circuit 110 mayperform some or all the operations described herein.

Method 900 begins at block 905 where processing logic performing themethod receives an application of power supply 116. The application ofpower supply 116 may be at power-up. At block 910, processing logiccontrols switch circuit 112 to connect power supply 116 to processingdevice 118. At block 915, processing logic receives, from processingdevice 118 via control interface 220, control information to configurecapacitance sensing circuit 110. At block 920, processing logicconfigures capacitance sensing circuit 110 with the control information.The control information indicates events capacitance sensing circuit 110is to connect or disconnect power supply 116 and processing device 118.

At block 925, processing device disconnects, subsequent to receiving thecontrol information, power supply 116 from processing device 118. Itshould be appreciated that method 900 may incorporate some or all of theoperations of method 800. For example, after block 925, processing logicmay operate the capacitance sensing circuit 110 in an idle state. Afteran interval, processing logic may operate capacitance sensing circuit110 in an active state and move to block 930. At block 930, processinglogic may measure a signal indicative of a capacitance of a touch button114 to detect a presence of a touch object. In one embodiment, apresence of a touch object may be measured on one or more touch buttonsindividually. In another embodiment, multiple touch buttons may becoupled together to form a composite button. Processing logic maymeasure a signal indicative of the capacitance of the composite buttonto detect a presence of a touch object proximate to the compositebutton. It should be appreciated that if no presence of a touch objectis detected, processing logic may return capacitance sensing circuit 110to an idle state. If a presence of a touch object is detected,processing logic may continue to block 930. At block 930, processinglogic connects power supply 116 to processing device 118 in response todetecting a presence of a touch object. In another embodiment,processing logic may control switch circuit 112 to connect power supply116 to processing device 118 in response to a timer event andindependent of a detected presence of a touch object.

FIG. 9B is a flow diagram illustrating the operation of a low-powertouch button sensing system, according to another embodiment. Method 950may be performed by processing logic that comprises hardware (e.g.,circuitry, dedicated logic, programmable logic, microcode), software(e.g., instructions run on a processing device to perform hardwaresimulation), or a combination thereof. In one embodiment, low-powertouch button circuit 101 and or capacitance sensing circuit 110 mayperform some or all the operations described herein.

Method 950 begins at block 955 where processing logic performing themethod receives an application of power supply 116. The application ofpower supply 116 may be at power-up. At block 960, processing logic, inresponse to the application of power supply 116, automatically controlsswitch circuit 112 to connect power supply 116 to processing device 118.At block 965, processing logic receives, from processing device 118 viaa control interface 220, control information to configure capacitancesensing circuit 110 to sense multiple touch buttons as a compositebutton. At block 970, processing logic configures capacitance sensingcircuit 110 to sense a composite button (e.g., detect a presence of atouch object proximate the composite button). At block 975, processinglogic receives a command, via control interface 220, to disconnect powersupply 116 from processing device 118 (e.g., by controlling switchcircuit 112). At block 980, processing logic, in response to thecommand, controls switch circuit 112 to disconnect power supply 116 fromprocessing device 118.

At block 985, processing logic detects a presence of a touch objectproximate to the composite button. As described above, the capacitancesensing circuit 110 may be operating in a normal mode or continuous modeto detect a presence of a touch object. At block 990, processing logic,responsive to detecting a presence of a touch object proximate thecomposite button, controls switch circuit 112 to connect power supply116 to processing device 118. At block 995, processing logic sendscontrol information to capacitance sensing circuit 110 via controlinterface 220 to configure capacitance sensing circuit 110 to sense thetouch buttons individually (e.g., detect a presence of a touch objectproximate each touch button individually). Capacitance sensing circuit110 may operate in normal mode or continuous mode to sense the touchbuttons individually. At block 999, processing logic may send themeasurement values of each individual touch button to processing device118. Processing logic may send raw measurement values or stateinformation of the individual buttons, or other information indicativeof the measurement of the touch buttons. State information for eachtouch button may indicate a touch event or non-touch event on therespective touch button as determined by, for example, state machine 342of capacitance sensing circuit 110.

FIG. 10 is a block diagram illustrating an electronic system including aprocessing device and low-power touch button circuit, according toanother embodiment. Processing device 1010 may perform the same orsimilar functions as described with respect to processing device 118 ofthe above Figures, and vice versa. Capacitive sense array 1025 mayinclude on or more touch buttons, as described above. In anotherembodiment, low-power touch button circuit 101 may be external toprocessing device 1010. The processing device 1010 and or low-powertouch button circuit 101 is configured to detect one or more presencesof a touch object detected proximate to a touch-sensing device, such ascapacitive sense array 1025. The processing device 1010 and or low-powertouch button circuit 101 may detect conductive objects, such as passivetouch object 1040 (e.g., fingers and or passive stylus 1030, or anycombination thereof). The low-power touch button circuit 101 may measuretouch data created by a presence of a touch object using the capacitivesense array 1025. The presence of a touch object may be detected by asingle or multiple sensing cells, each cell representing an isolatedsense element or an intersection of sense elements (e.g., electrodes) ofthe capacitive sense array 1025. In one embodiment, when the low-powertouch button circuit 101 measures a signal indicative of mutualcapacitance of the touch-sensing device (e.g., using capacitive sensearray 1025), the low-power touch button circuit 101 acquires a 2Dcapacitive image of the touch-sensing object and processes the data forpeaks and positional information. In another embodiment, the processingdevice 1010 is a microcontroller that obtains a capacitance touch signaldata set from application processor 1050, and finger detection firmwareexecuting on the microcontroller identifies data set areas that indicatetouches, detects and processes peaks, calculates the coordinates, or anycombination therefore. The microcontroller may report the precisecoordinates to an application processor 1050, as well as otherinformation.

Electronic system 1000 includes processing device 1010, capacitive sensearray 1025, passive stylus 1030, and application processor 1050. Thecapacitive sense array 1025 may include capacitive sense elements thatare electrodes of conductive material, such as copper. The conductivematerial may painted or otherwise attached onto a substrate and orelectrodes. The sense elements may also be part of an indium-tin-oxide(ITO) panel. The capacitive sense elements may be used to allow thelow-power touch button circuit 101 to measure self-capacitance, mutualcapacitance, passive touch detection, other types of touch detection, orany combination thereof. In the depicted embodiment, the electronicsystem 1000 includes the capacitive sense array 1025 coupled to theprocessing device 1010 via bus 1022. The capacitive sense array 1025 mayinclude a multi-dimension capacitive sense array. The multi-dimensionsense array includes multiple sense elements, organized as rows andcolumns. In another embodiment, the capacitive sense array 1025 isnon-transparent capacitive sense array (e.g., PC touchpad). Thecapacitive sense array 1025 may be disposed to have a flat surfaceprofile. Alternatively, the capacitive sense array 1025 may havenon-flat surface profiles. Alternatively, other configurations ofcapacitive sense arrays may be used. For example, instead of verticalcolumns and horizontal rows, the capacitive sense array 1025 may have ahexagon arrangement, or the like, as would be appreciated by one ofordinary skill in the art having the benefit of this disclosure. In oneembodiment, the capacitive sense array 1025 may be included in an ITOpanel or a touch screen panel.

The operations and configurations of the processing device 1010 and orlow-power touch button circuit 101 and the capacitive sense array 1025for detecting and tracking the passive touch object 1040 are describedherein. In short, the processing device 1010 and or low-power touchbutton circuit 101 is configurable to detect a presence of the passivetouch object 1040 on the capacitive sense array 1025.

In the depicted embodiment, the processing device 1010 includes analogand or digital general purpose input/output (“GPIO”) ports 1007. GPIOports 1007 may be programmable. GPIO ports 1007 may be coupled to aProgrammable Interconnect and Logic (“PIL”), which acts as aninterconnect between GPIO ports 1007 and a digital block array (notshown) of the processing device 1010. The digital block array may beconfigurable to implement a variety of digital logic circuits (e.g.,DACs, digital filters, or digital control systems) using, in oneembodiment, configurable user modules (“UMs”). The digital block arraymay be coupled to a system bus. Processing device 1010 may also includea memory device, such as random access memory (“RAM”) 1005 and programflash 1004. RAM 1005 may be static RAM (“SRAM”), and program flash 1004may be a non-volatile storage, which may be used to store firmware(e.g., control algorithms executable by processing core 1009 toimplement operations described herein). Processing device 1010 may alsoinclude a memory controller unit (“MCU”) 1003 coupled to memory and theprocessing core 1009. The processing core 1009 is a processing elementconfigured to execute instructions or perform operations. The processingdevice 1010 may include other processing elements as would beappreciated by one of ordinary skill in the art having the benefit ofthis disclosure. It should also be noted that the memory may be internalto the processing device or external to it. In the case of the memorybeing internal, the memory may be coupled to a processing element, suchas the processing core 1009. In the case of the memory being external tothe processing device, the processing device is coupled to the otherdevice in which the memory resides as would be appreciated by one ofordinary skill in the art having the benefit of this disclosure.

In one embodiment, the processing device 1010 and or low-power touchbutton circuit 101 further includes processing logic 1002. Some or allof the operations of the processing logic 1002 may be implemented infirmware, hardware, or software or some combination thereof. Theprocessing logic 1002 may receive signals from the low-power touchbutton circuit 101, and determine the state of the capacitive sensearray 1025, such as whether an passive touch object 1040 (e.g., afinger) is detected on or in proximity to the capacitive sense array1025 (e.g., determining the presence of the object), resolve where thepassive touch object 1040 is on the sense array (e.g., determining thelocation of the passive touch object 1040), tracking the motion of thepassive touch object 1040, or other information related to an passivetouch object 1040 detected at the touch sensor. In another embodiment,processing logic 1002 may include low-power touch button circuit 101. Inanother embodiment, processing logic 1002 may perform some or all thefunctions of low-power touch button circuit 101 and or processing device1010.

The processing device 1010 may also include an analog block array (notshown) (e.g., field-programmable analog array). The analog block arrayis also coupled to the system bus. Analog block array may also beconfigurable to implement a variety of analog circuits (e.g., ADCs oranalog filters) using, in one embodiment, configurable UMs. The analogblock array may also be coupled to the GPIO 1007.

As illustrated, low-power touch button circuit 101 may be integratedinto processing device 1010. Low-power touch button circuit 101 mayinclude analog I/O for coupling to an external component, such astouch-sensor pad (not shown), capacitive sense array 1025, touch-sensorslider (not shown), touch-sensor buttons (not shown), and or otherdevices. The low-power touch button circuit 101 may be configurable tomeasure a signal indicative of capacitance using mutual-capacitancetouch detection techniques, self-capacitance touch detection techniques,passive touch detection techniques, charge-coupling techniques, chargebalancing techniques, or the like. In one embodiment, low-power touchbutton circuit 101 operates using a charge accumulation circuit, acapacitance modulation circuit, or other capacitance sensing methodsknown by those skilled in the art. In an embodiment, the low-power touchbutton circuit 101 is of the Cypress TMA-3xx, TMA-4xx, or TMA-xxfamilies of touch screen controllers. Alternatively, other low-powertouch button circuits may be used. The mutual capacitive sense arrays,or touch screens, as described herein, may include a transparent,conductive sense array disposed on, in, or under either a visual displayitself (e.g. LCD monitor), or a transparent substrate in front of thedisplay. In an embodiment, the transmission (TX) and receiving (RX)electrodes are configured in rows and columns, respectively. It shouldbe noted that the rows and columns of electrodes may be configured as TXor RX electrodes by the low-power touch button circuit 101 in any chosencombination. In one embodiment, the TX and RX electrodes of the sensearray 1025 are configurable to operate as a TX and RX electrodes of amutual capacitive sense array in a first mode to detect passive touchobjects, and to operate as electrodes of a coupled-charge receiver in asecond mode to detect a stylus on the same electrodes of the sensearray. An intersection between two sense elements may be understood as alocation at which one sense electrode crosses over or overlaps another,while maintaining galvanic isolation from each other. The capacitanceassociated with the intersection between a TX electrode and an RXelectrode may be sensed by selecting every available combination of TXelectrode and RX electrode. When a passive touch object 1040 approachesthe capacitive sense array 1025, the object causes a decrease in mutualcapacitance between some of the TX/RX electrodes. In another embodiment,the presence of a finger increases the capacitance of the electrodes tothe environment (Earth) ground, typically referred to asself-capacitance change. Utilizing the change in mutual capacitance, thelocation of the finger on the capacitive sense array 1025 may bedetermined by identifying the RX electrode having a decreased couplingcapacitance between the RX electrode and the TX electrode to which theTX signal was applied at the time the decreased capacitance was measuredon the RX electrode. Therefore, by sequentially measuring signals todetermine measurements representing the capacitances associated with theintersection of electrodes, the locations of one or more touch objectsmay be determined. It should be noted that the process may calibrate thesense elements (intersections of RX and TX electrodes) by determiningbaselines for the sense elements. It should also be noted thatinterpolation may be used to detect finger position at betterresolutions than the row/column pitch as would be appreciated by one ofordinary skill in the art having the benefit of this disclosure. Inaddition, various types of coordinate interpolation algorithms may beused to detect the center of the touch as would be appreciated by one ofordinary skill in the art having the benefit of this disclosure.

Processing device 1010 and or low-power touch button circuit 101 mayinclude internal oscillator/clocks 1006 and communication block (“COM”)1008. In another embodiment, the processing device 1010 includes aspread-spectrum clock (not shown). The oscillator/clocks block 1006provides clock signals to one or more of the components of processingdevice 1010. Communication block 1008 may be used to communicate with anexternal component, such as an application processor 1050, viaapplication interface (“I/F”) line 1051.

Processing device 1010 and or low-power touch button circuit 101 mayreside on a common carrier substrate such as, for example, an integratedcircuit (“IC”) die substrate, a multi-chip module substrate, or thelike. Alternatively, the components of processing device 1010 may be oneor more separate integrated circuits and or discrete components. In oneexemplary embodiment, processing device 1010 is the Programmable Systemon a Chip (PSoC®) processing device, developed by Cypress SemiconductorCorporation, San Jose, Calif. Alternatively, processing device 1010 maybe one or more other processing devices known by those of ordinary skillin the art, such as a microprocessor or central processing unit, acontroller, special-purpose processor, digital signal processor (“DSP”),an application specific integrated circuit (“ASIC”), a fieldprogrammable gate array (“FPGA”), or the like.

It should also be noted that the embodiments described herein are notlimited to having a configuration of a processing device coupled to anapplication processor, but may include a system that measures a signalindicative of the capacitance on the sensing device and sends the rawdata to a host computer where it is analyzed by an application. Ineffect, the processing that is done by processing device 1010 may alsobe done in the application processor.

Low-power touch button circuit 101 may be integrated into the IC of theprocessing device 1010, or alternatively, in a separate IC.Alternatively, descriptions of low-power touch button circuit 101 may begenerated and compiled for incorporation into other integrated circuits.For example, behavioral level code describing the low-power touch buttoncircuit 101, or portions thereof, may be generated using a hardwaredescriptive language, such as VHDL or Verilog, and stored to amachine-accessible medium (e.g., CD-ROM, hard disk, floppy disk, etc.).Furthermore, the behavioral level code may be compiled into registertransfer level (“RTL”) code, a netlist, or even a circuit layout andstored to a machine-accessible medium. The behavioral level code, theRTL code, the netlist, and the circuit layout may represent variouslevels of abstraction to describe low-power touch button circuit 101.

It should be noted that the components of electronic system 1000 mayinclude all the components described above. Alternatively, electronicsystem 1000 may include some of the components described above.

In one embodiment, the electronic system 1000 is used in a tabletcomputer. Alternatively, the electronic device may be used in otherapplications, such as a notebook computer, a mobile handset, a personaldata assistant (“PDA”), a keyboard, a television, a remote control, amonitor, a handheld multi-media device, a handheld media (audio and orvideo) player, a handheld gaming device, a signature input device forpoint of sale transactions, an eBook reader, global position system(“GPS”) or a control panel. The embodiments described herein are notlimited to touch screens or touch-sensor pads for notebookimplementations, but may be used in other capacitive sensingimplementations, for example, the sensing device may be a touch-sensorslider (not shown) or touch-sensor buttons (e.g., capacitance sensingbuttons). In one embodiment, these sensing devices include one or morecapacitive sensors or other types of capacitance-sensing circuitry. Theoperations described herein are not limited to notebook pointeroperations, but may include other operations, such as lighting control(dimmer), volume control, graphic equalizer control, speed control, orother control operations requiring gradual or discrete adjustments. Itshould also be noted that these embodiments of capacitive sensingimplementations may be used in conjunction with non-capacitive sensingelements, including but not limited to pick buttons, sliders (ex.display brightness and contrast), scroll-wheels, multi-media control(ex. volume, track advance, etc.) handwriting recognition, and numerickeypad operation.

Certain embodiments may be implemented as a computer program productthat may include instructions stored on a machine-readable medium. Theseinstructions may be used to program a general-purpose or special-purposeprocessor to perform the described operations. A machine-readable mediumincludes any mechanism for storing or transmitting information in a form(e.g., software, processing application) readable by a machine (e.g., acomputer). The machine-readable medium may include, but is not limitedto, magnetic storage medium (e.g., floppy diskette); optical storagemedium (e.g., CD-ROM); magneto-optical storage medium; read-only memory(ROM); random-access memory (RAM); erasable programmable memory (e.g.,EPROM and EEPROM); flash memory; or another type of medium suitable forstoring electronic instructions.

Additionally, some embodiments may be practiced in distributed computingenvironments where the machine-readable medium is stored on and orexecuted by more than one computer system. In addition, the informationtransferred between computer systems may either be pulled or pushedacross the communication medium connecting the computer systems.

Although the operations of the methods herein are shown and described ina particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operation may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be in an intermittent andor alternating manner. The terms “first,” “second,” “third,” “fourth,”etc. as used herein are meant as labels to distinguish among differentelements and may not necessarily have an ordinal meaning according totheir numerical designation. As used herein, the term “coupled” may meanconnected directly or indirectly through one or more interveningcomponents. Any of the signals provided over various buses describedherein may be time multiplexed with other signals and provided over oneor more common on-die buses. Additionally, the interconnection andinterfaces between circuit components or blocks may be shown as buses oras single signal lines. Each of the buses may alternatively be one ormore single signal lines and each of the single signal lines mayalternatively be buses.

The above description sets forth numerous specific details such asexamples of specific systems, components, methods, and so forth, inorder to provide an understanding of several embodiments of the presentinvention. It may be apparent to one skilled in the art, however, thatat least some embodiments of the present invention may be practicedwithout these specific details. In other instances, well-knowncomponents or methods are not described in detail or are presented insimple block diagram format in order to avoid unnecessarily obscuringthe present invention. Thus, the specific details set forth are merelyexemplary. Particular implementations may vary from these exemplarydetails and still be contemplated to be within the scope of the presentinvention.

What is claimed is:
 1. A method, comprising: receiving, by a capacitancesensing circuit, an application of a power supply that powers thecapacitance sensing circuit; controlling, by the capacitance sensingcircuit, a switch circuit to connect the power supply to a processingdevice responsive to the application of the power supply; receiving,from the processing device via a control interface, control informationto configure the capacitance sensing circuit; and responsive toreceiving the control information to configure the capacitance sensingcircuit from the processing device, disconnecting the power supply fromthe processing device.
 2. The method of claim 1, wherein controlling theswitch circuit to connect the power supply to the processing device isautomatically responsive to receiving the application of the powersupply.
 3. The method of claim 1, further comprising: measuring a signalindicative of a capacitance of a touch button to detect a presence of atouch object proximate to the touch button, the touch button operativelycoupled to the capacitance sensing circuit; and connecting the powersupply to the processing device in response to detecting the presence ofthe touch object.
 4. The method of claim 3, wherein measuring the signalindicative of the capacitance of the touch button to detect the presenceof the touch object proximate to the touch button occurs at intervals.5. The method of claim 1, further comprising: controlling, by thecapacitance sensing circuit, the switch circuit to connect the powersupply to the processing device responsive to a timer event andindependent of a presence of a touch object detected proximate to atouch button.
 6. The method of claim 1, further comprising: configuringthe capacitance sensing circuit with the control information, whereinthe control information configures the capacitance sensing circuit toconnect or disconnect the power supply and the processing device inresponse to events.
 7. The method of claim 1, further comprising:coupling a plurality of touch buttons to form a composite button; andmeasuring a signal indicative of a capacitance of the composite buttonto detect a presence of a touch object proximate to the compositebutton.
 8. An apparatus, comprising: a capacitance sensing circuit,operatively coupled to a touch button, to control power supplied to aprocessing device using a switch circuit, wherein the capacitancesensing circuit, responsive to an application of a power supply thatpowers the capacitance sensing circuit, to cause the power supply to beconnected with the processing device, wherein the capacitance sensingcircuit to receive, from the processing device via a control interface,control information to configure the capacitance sensing circuit, andwherein responsive to receiving the control information to configure thecapacitance sensing circuit from the processing device, the capacitancesensing circuit to disconnect the power supply from the processingdevice.
 9. The apparatus of claim 8, wherein the capacitance sensingcircuit further comprises: the control interface to provide an interfaceto exchange information to and from the capacitance sensing circuit. 10.The apparatus of claim 8, wherein the capacitance sensing circuit todisconnect a power supply from the processing device until, responsiveto a presence of a touch object is detected proximate to the touchbutton, the capacitance sensing circuit to connect the power supply tothe processing device.
 11. The apparatus of claim 8, wherein thecapacitance sensing circuit is unresponsive to a presence of a touchobject proximate to one or more other touch buttons.
 12. The apparatusof claim 8, wherein the capacitance sensing circuit further comprises:an analog front end (AFE) to measure a signal indicative of acapacitance of the touch button indicative of a presence of a touchobject; a bias generator, oscillator, timer (BOT) circuit to generate aclock signal; and a control circuit, responsive to receiving the clocksignal, to turn on the AFE to measure the signal indicative of thecapacitance of the touch button.
 13. The apparatus of claim 8, whereinthe capacitance sensing circuit further comprises: a delay timer circuitto cause the capacitance sensing circuit to connect the power supply tothe processing device independent of a presence of a touch objectdetected proximate to the touch button.
 14. The apparatus of claim 8,wherein the capacitance sensing circuit is to be configured, via thecontrol interface, with the control information, wherein the controlinformation configures the capacitance sensing circuit to connect ordisconnect the power supply and the processing device in response toevents, wherein the control interface comprises a serial interface. 15.The apparatus of claim 8, wherein the capacitance sensing circuitfurther comprises: a plurality of button switches to connect thecapacitance sensing circuit to a plurality of touch buttons, wherein atleast two or more of the plurality of touch buttons, using at least twoor more of the plurality of switches, to be electrically coupled to forma composite button, wherein the capacitance sensing circuit to measure asignal indicative of a capacitance of the composite button.
 16. Theapparatus of claim 8, wherein the touch button comprises a capacitivebutton operatively coupled to the capacitance sensing circuit.
 17. Amethod, comprising: receiving, by a capacitance sensing circuit, anapplication of a power supply that powers the capacitance sensingcircuit; responsive to receiving control information to configure thecapacitance sensing circuit from the processing device, disconnectingthe power supply from the processing device; detecting, by thecapacitance sensing circuit, a presence of a touch object proximate to atouch button; and controlling, by the capacitance sensing circuit, aswitch circuit to connect the power supply to the processing deviceresponsive to the detected presence of the touch object, wherein thecapacitance sensing circuit consumes an average of less than 100nanoamperes during operation.
 18. The method of claim 17, furthercomprising: receiving, by the capacitance sensing circuit, theapplication of the power supply at power-up; controlling, by thecapacitance sensing circuit, the switch circuit to connect the powersupply to the processing device; receiving, from the processing devicevia a control interface, control information to configure thecapacitance sensing circuit; and disconnecting, subsequent to receivingthe control information, the power supply from the processing device.19. The method of claim 17, further comprising: coupling a plurality oftouch buttons to form a composite button; and measuring a signalindicative of a capacitance of the composite button to detect thepresence of the touch object proximate to the composite button.
 20. Themethod of claim 17, further comprising: controlling, by the capacitancesensing circuit, the switch circuit to connect the power supply to theprocessing device responsive to a timer event and independent of thepresence of the touch object detected proximate to the touch button.